[48.12] Production of Light p-Process Isotopes in Neutrino-Irradiated Alpha-Rich Freezeouts

The origin of the light, neutron-capture bypassed
(p-process) isotopes 92Mo, 94Mo, 96Ru, and
98Ru has long been a mystery. Sites that produce the
majority of the p-process isotopes in correct solar
proportions have long been known to underproduce the light
species [1], thereby suggesting a different origin. The
alpha-rich freezeout occurring near a nascent neutron star
in Type II supernovae has been proposed [2,3,4]; however,
only 92Mo is strongly produced, and it is never the
most overproduced isotope, as is required for its site of
origin. We explore models of alpha-rich freezeouts that
include simultaneous irradiation of the nuclei by the
copious neutrinos emitted during the explosion. We find that
neutrino-nucleus interactions significantly enhance
production of the light p-process species both by affecting
the electron-nucleon ratio during the nucleosynthesis and by
increasing the charge of nuclei once nuclear
quasi-equilibrium clusters have broken. In many models
studied, the light p-process isotopes are the most
overproduced species, which supports the idea of this being
a possible production site. The neutrino fluences required
for light p-process isotope production are high--probably
somewhat higher than current supernova models allow.
Nevertheless, the results are encouraging and suggest
further work is needed on this promising site.

This work was supported by the NSF Research Experiences for
Undergraduates (REU) Site Program through grant AST 96169939
to Florida Tech and the Southeastern Association for
Research in Astronomy (SARA). It was also supported by NSF
grant AST 9819877 and NASA grant NAG5-4703 at Clemson
University.